1. Field of the Invention
The present invention relates generally to improved means and techniques for detecting the presence of spot defects such as areas of discoloration, pits or seeds or fragments thereof in fruit, and, more particularly, to improved means and techniques for detecting the presence of such an area anywhere on a fruit, or a peach pit or pit fragments in the pit cavity of a peach half, and for classifying the fruits or peach halves according to the presence, size or number of discolored areas or pit fragments detected.
2. Description of the Prior Art
In the processing of peaches in peach canneries, the peaches are usually cut in half by a saw or knife, and the peach pit is removed by a pitter. Following this, the outer skin of the peach is removed and each of the halves is then delivered to an inspection station for detection of blemishes, discoloration, pits, and pit fragments prior to canning. The operation of the peach pitter, while generally satisfactory, is not perfect, and as a result many of the peach halves still retain a pit or a fragment of a pit. Peach halves which contain pits or pit fragments are undesirable due to the potential injury posed to a consumer's teeth. Consequently, it is important to provide an inspection means for assuring that no peach halves are canned which contain any pit or pit fragments.
In the past, the inspection of peach halves was accomplished by means of visual observation and manual removal. This technique, in order to be reasonably satisfactory, necessitated the employment of many inspectors at considerable expense. A further problem associated with the use of people as inspectors is that the inspectors are prone to fatigue, especially when engaged in repetitive inspection activity. Consequently, some of the peaches containing pit fragments will not be removed from the batch of peach halves and will be canned. Due to the aforementioned factors, a sampling inspection routine is frequently used wherein less then all of the peach halves are inspected.
Another prior art technique used in the detection of peach pits and pit fragments in peach halves involves illuminating the peach half cavity and measuring the amount of light transmitted therethrough. Basically, this method involves the use of transmitted light to effect a contrast between a peach half free of fragments and a peach half having a pit fragment within the area scanned by a slit placed between a photocell and the peach half. Such a system is described in U.S. Pat. No. 3,005,549, Flanders et al, entitled "Peach Pit Fragmentation Detection Means and Techniques". However, as pointed out in this patent, one of the significant limitations imposed by the use of this particular method is that the size of pit fragment detectable is limited to a fragment no smaller than about one-eighth the size of the whole pit. Further, it should be noted that the operation of this particular device as disclosed by Flanders et al is dependent on the particular position of a pit fragment. The reason given in the patent for this position sensitivity is that only a portion of the average diameter of the pit cavity is scanned. Therefore, it is quite possible that a peach pit fragment may go undetected in the cavity when using the Flanders et al apparatus, and, as a result, the peach half containing a pit or pit fragment will not be culled, i.e., discharged as unacceptable. The degree of detector resolution and cavity inspection discussed above is unacceptable by present standards, because a peach pit fragment of a size smaller than about one-eighth the size of the whole pit can cause severe injury to a consumer's teeth, thereby incurring legal liability for the canner.
Another prior art patent, U.S. Pat. No. 2,823,800, Bliss, is of interest in the discussion of the subject matter of the instant invention. The Bliss patent relates to an egg inspection machine, generally referred to as an "automatic candler". Such a machine non-destructively inspects eggs to cull those eggs containing spots of blood therein. The Bliss machine teaches the use of two different strobed light sources transmitting relatively narrow bands of light wavelengths to illuminate the egg to be inspected. One of the light wavelength bands is selected so that the amount of light transmitted through the egg is relatively unaffected by the presence or absence of blood in the egg. The other of the light wavelength bands is selected because its transmission through the egg is substantially affected by the presence of blood in the egg. The amount of light transmitted through the egg in the two different bands is alternately sensed by a phototube. The phototube output is fed to the control grids of a pair of triodes arranged in a circuit to function as a differentially balanced amplifier. When an egg containing blood is observed, the amplifier circuit becomes unbalanced, allowing current to flow through a relay coil. The relay operates to close a switch, energizing a solenoid-operated discharge paddle which discharges the egg. This circuit arrangement requires that the circuit be periodically balanced to assure proper operation. A further limitation of the Bliss system lies in the fact that it does not provide any means for adjusting the resolution of the machine so that it can detect very small blood spots. Another restrictive characteristic inherent in this device is the necessity for the inspected item to be translucent so that light may be transmitted through the object. Additionally, a variation in transparency and/or density in the inspected item requires adjustment in the intensity of the light source to assure that sufficient light is transmitted through the inspected item for adequate sensitivity.
It may be seen that a discoloration area, pit or pit fragment detector is required which has sufficiently fine resolution to detect smaller discolored areas or pit fragments, and which is continuously on-line to thereby provide inspection for 100% of the fruit or fruit sections passing there-along.